1. Field of the Invention
This invention generally relates to a method of generating absolute time in pregroove (ATIP) data, and more particularly to a method of generating ATIP data based on an original ATIP data signal generated by a wobble signal and an ATIP clock signal.
2. Description of Related Art
During the manufacture of the re-writable compact disk (CR-RW), a shallow groove is made to spiral from the center of the CD-RW toward the outer circumference. This groove is referred to as a pregroove. This pregroove is not a perfect spiral but includes a little wobbling. Generally, in a compact disk (CD) made by die-casting, each sector includes the timing-related data to control the spin speed of the CD-ROM drive in order to accurately read the data on the CD. A CD-RW drive must have some way to control the laser when recording the data and to control the spin speed. The wobbling pregroove provides ATIP data which may be used to control the tracking and timing of the CD-RW drive.
The wobbling shape of the pregroove is similar to a sinusoid and has a track excursion deviation range of 0.03 um from the centerline of the data recording track. This range is 1/1000 of the wavelength of the pregroove. That is why the pregroove is referred to as “wobbling”. Although the pregroove is almost invisible, the optical driving device of the CD-RW drive can detect the pregroove and use the pregroove to guide the laser beam of the CD-RW drive and to provide ATIP data for ensuring a stable data recording speed.
Therefore, how to effectively read the wobble signal from the CD-RW and to effectively obtain the ATIP data from the wobble signal is an important issue in CD-RW applications.